The present invention relates to a planet carrier assembly.
Traditional wind turbine gearboxes involve the use of one or more planetary gear sets to reduce the torque and increase the speed of the power supplied by the rotor. One disadvantage of using a planetary gear set in high power applications is the load that planet gears and bearings must take is quite large. A current solution to this problem is to increase the number of planets in the gear set however this has the consequence of limiting the ratio achievable out of the set.
U.S. Pat. No. 7,090,465 (FIG. 1) suggests a method whereby additional planets are added to the system by the use of a double sided carrier (or bogie plate). This has the advantage of reducing the load on the planet gears and bearings while allowing higher ratio's to be achieved. The design claimed however has the disadvantage of requiring a common pin 44 for each opposing pair of planet gears 47. Consequently the planet gears on each side of the carrier are not completely independent and loads on one planet gear will affect the gears utilizing the common pin, this is of particular concern in flexible pin applications.
U.S. Pat. Appl. No. 2006/016055A1 (FIG. 1) discloses how an external force will cause a shaft of the so-called flexpin type, such as described in GB1101131, to bend as a result of a bending moment. A. The use of the flexible pin, or flexpin, 44 is advantageous for load distribution over the tooth flanks (KHβ) as well as load sharing between the planets in the planetary cell (Kγ). The equality of loads between the planets (Kγ) will be inversely proportional to the stiffness of the planet shafts and it is thus preferred to make the planet shafts as flexible as possible.